This invention generally relates to a tracking system which is employed in a video tape recorder/reproducer, and more particularly to a system for generating a displacing pattern signal applied to a positionable element on which a video head is mounted so as to maintain the video head in substantially undeviating condition with respect to a recorded video track.
Recently, an automatic tracking system has been introduced to a video tape recorder/reproducer. Such system makes possible a proper tracking of the video track recorded on a video tape, reproducing no noise band pictures at any tape speed modes, for example, normal speed mode, slow motion mode, still motion mode, quick motion mode, reverse motion mode and so on.
In the conventional automatic tracking system, video heads are mounted on positionable elements such as piezoelectric element. The positionable element is dithered by a signal from an oscillator. The tracking error signals are detected from the envelope of reproduced signals. According to resultant tracking error signal, a negative feedback (NFB) loop controls the positionable element so that the video head properly follows the recorded track.
In the case that the automatic tracking system described above is applied to a video recorder/reproducer employing a narrow video track width (for example, 20 micrometer), a displacing amplitude of the video head due to the dither signal is restricted within a few micrometer.
Accordingly, the tracking error signal obtained from the envelope signals becomes a signal having a very low S/N ratio. For the improvement of the low S/N ratio, it is necessary to use a L.P.F. having a very low cutoff frequency in the NFB loop. Since the transient response of the loop is limited by this L.P.F., some noise bars appear on the reproduced pictures during a reproduction mode change.